The invention relates to a method and an arrangement for monitoring a power output stage, the power output stage having at least one half-bridge, which comprises a series circuit comprising two semiconductor switches and has an operating voltage applied to it, it being possible for the semiconductor switches to be controlled alternately into an on state and an off state by pulse width-modulated pulses, and the junction point between the semiconductor switches of the at least one half-bridge forming an output.
It is necessary, in particular for safety-relevant applications in motor vehicles, for example for electrically assisted steering, to detect any fault which may lead to a hazardous state. In the case of electrically assisted steering systems, DC or EC motors are used for providing assistance which are controlled via an H bridge or a B6 bridge by applying pulse width-modulated pulses to the half-bridges. The semiconductor switching elements, usually MOSFETs, are driven by a control device (microcontroller or digital signal processor). For fault detection, continuous monitoring of the rms voltages applied at the output is necessary.